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Stockley Academy, Hillingdon, London

Sutherland Lyall talks to Aedas Architects' regional director Sarah Williams about its Stockley Academy, a public/private-financed city academy specialising in science and technology

Stockley Academy in London's Hillingdon is one of the new breed of specialist city academies that have public-private financing, often built as replacements for failing schools. This academy, one of several being designed by Aedas Architects, specialises in science and technology and is currently taking shape on the playing fields of the former Evelyns Community School. When the new building is completed in spring 2005, the old school will be demolished and its site seeded for games pitches. The name comes from the nearby pioneering commercial office development, Stockley Park.

Things have changed in the world of city academies since the Aedas team, under regional director Sarah Williams, won the job at interview. Now framework agreements are developed with a complete design team including architects, the various engineers and a cost consultant. At that time the design team was assembled by the client.

This is no criticism of the present Stockley team where the appointed engineer was Melliss & Partners, quantity surveyor Robinson Low Francis and M&E consultant FaberMaunsell.

Changing brief As one might expect with a new hybrid, there have been a number of interested parties.

The client was Stockley Academy Trust but everybody from the private sponsor through the Department for Education and Science and Sports England, to the head, staff, local residents, the planners and the specialist consultants concerned with such things as fire and acoustics, have had an input. Other effects on the brief included the need for these academies to be open for community use until early evening. This meant, said Williams, that: 'You had to think about the zoning so that parts could be used without opening up the rest of the building.' The new academy had to provide teaching areas for the three main subject groups: science and technology, communications and humanities, and maths and business.

In addition, there was a need for sports and drama facilities and the inevitable assembly hall. And there were site constraints. Williams says: 'One of the important things was that the client needed to retain the existing entrance to the north west for use by students, while creating a new entrance to the south. The idea was that staff and visitors could come in from a quiet side street.'

Planning for clarity The plan that Aedas came up with was based on the need for clarity of entrance and circulation 'so you always knew where you were', Williams says. There is an E-shaped block on the east, with one two-storey leg for each specialism, including a doubleheight resource centre in each. On the west is a linear building, the double-height sports and drama block, with its high-ceilinged gym and drama spaces. This building is half buried to minimise visual intrusion.

These two blocks, one a tight massing of smallish rooms, the other a small number of big volumes, are connected by a long trapezoidal entrance atrium with sawtooth north lights and glass walls. Giving access from both north and south into this space solved the problem of coping with two main entrances and, since the drama and gym areas are those which will be most used by the locals out of school hours, it also solved the problem of security: the school can simply lock the doors leading into the E block.

There are dining and social spaces in the double-height atrium, which will be divided by a big sliding glass screen. When the screen is drawn back, the two spaces can be used together for assemblies and formal functions. At the south end of the physical arts block, there is another oval assembly hall with bleacher seating.

There was some early discussion about flexibility. But, says Williams: 'When we went through the brief it was clear that such things as the technical teaching areas are more or less standard. We started off with ideas about being able to make rooms bigger or smaller with demountable partitions. But there are onerous acoustic requirements in schools. Then there were discussions about blockwork or drylining on studs, and in the end the walls are mostly blockwork because the likelihood of change was low - but change could still be achieved.'

Outsourcing NBS An unusual additional member of the team was Schumann Smith, a practice that specialises in preparing NBS specifications.

Williams says: 'We choose the materials and they pull it all together in the NBS. It means we have ownership of the specification but they compile it. Naturally we have agreement from the client, and it is an arrangement that is becoming quite common.' Aedas also outsources some of its high-end 3D visualisation and all of its modelmaking. It uses the industry standard AutoCAD 2000 and 3D StudioMAX.

This is a JCT 98 contract with a contractor-design portion supplement. That is, it is a conventional contract with the architect as the lead consultant and with the contractor, in this case Costain Construction, signed up to do the detail design work and take on some of the liabilities for the cladding package and, Williams, says, 'maybe the roof'.

Hollow core The structure is conventional in the sense that, even for the half-buried drama and gym block which has some steel superstructure, the foundations are piled, there is a ground-floor slab supported by concrete ground beams, and walls are generally of blockwork, in the case of external walls with rendered outer and inner plastered leaf.

The unusual feature is that in the teaching blocks the roof and first-floor slabs are made up from TermoDeck hollow-core planks, which form an essential element in the environmental controls. The TermoDeck planks are about 1,200 mm wide, with five circular cores running their lengths. At Stockley Academy, they span 9m between the structural corridor wall and the external walls.

The basic M&E strategy is to use the TermoDeck environmental control system, which is based on thermal mass. The builtin tubes can be connected laterally in the factory to circulate air through and between the planks that make up the slab. Registers can be installed over holes in the underside of the slab to provide fresh, mostly warmed, air in rooms. Pushing the air around inside heats up the slab, which then acts as a thermal sink, radiating warmth into the rooms below. Williams says: 'It has been used on the Elisabeth Fry building in Norwich, where it really helped to reduce the running costs. It worked amazingly well.' Project associate Geoff Davies adds: 'It is an economic installation and avoids the need for radiators. Having looked at various systems, the client's project manager decided that this was the most appropriate.' TermoDeck produces the design, and licenses Tarmac Topfloor in the UK and Ireland to produce the planks, implement the whole system, and take full responsibility for testing. At Stockley Academy, TermoDeck is used, as it normally is, as a ceiling delivery system: the ground floor is a solid slab.

An essential part of this M&E mix is the classroom glazing. Sampson Windows made the windows to the triple-glazing specification set by TermoDeck which calls for a single external skin of glass with an air gap containing an interstitial blind.

On the inside is a sealed double glazed unit.

Davies says: 'We were looking ideally for a triple glazed curtain wall until we found the Sampson system. It has powder-coated aluminium on the outside of the frames, and internally it is timber. For the non-TermoDeck areas, we have gone for a Sch³co double-glazed walling system installed by M Price. At the moment we may decide on louvres by a manufacturer we have used in the past. But the spec for this may change.

The roof lights to the sawtooth roof over the atrium are also by Sch³co.'

Keeping the lid on Davies says: 'We wanted a single-ply membrane for the roof. The design had moved on from the time when the roofs were more pitched. But via value engineering we moved to the current flat roofs, and we felt that in terms of performance and aesthetics we should go with Trocal or Sarnafil. Whichever, we don't want to use felt. But now we are researching an alternative which is more environmentally friendly and it appears to have an equivalent specification. Sarnafil and Trocal may simply be the easy option because they are good. We've used both, so we have no strong feeling but Sarnafil is in the spec. But there's not much in it.'

Building up the skin External finishes are generally a standard 12.5mm-thick coloured sand-cement render, with details in 440mm x 215mm x 100mm terracotta-faced blockwork from NBS Group. Davies says: 'We are using two types of block - black matt Avellino with a dark grouting for the three-course groundlevel plinth, with areas on the sports building which are Portland - the colour of Portland stone, a little rougher in texture and laid in stack bond'.

At the ends of the wings and between windows, the architect has specified Trespa facade cladding board of around 10mm thickness.

Davies says: 'We were looking at a wood effect panel and Prodema Lignum cladding panels with a melamine-faced surface. Trespa is made up so that the colour you see is actually the paper in the sandwich of timber and resin, and it allows a greater range of colour.

The actual look of the panel can be different because they have a range of finishes: mirror, matt and so on. Generally it's going to be used externally as a rain screen.

So far, so relatively conventional. But, Davies says: 'We have this egg-shaped hall, and we wanted something different. After researching a lot of oddly shaped buildings, Rheinzink zinc-clad lead seemed to lend itself to our hall. We liked it, and the details of the standing seam seemed to make it a more subtly detailed product. The seam we will use hasn't actually been worked out yet, but it will go down at 45°, so the physical way they do the standing seam is going to be interesting.'

Tough inside Davies explains, 'You have to specify tougher materials for schools, so it's hard wearing we want. The carpet tiles we specify, generally Tarkett polypropylene, provide wear qualities appropriate to a school installation.' The atrium floor is a Junckers timber laminate, which will be polished not stained.

'Corridors and classrooms are currently specified as being plastered and painted, but we are now looking at superior finishes for corridors, ' says Davies. Sto does a variety of finishes, and we are looking at them for corridors and also the atrium. It could be a kind of polished plaster finish rather than the current painted hard plaster.' The sports hall floor will be a new product, DD Linotop from Armstrong Floor Products. This is a sandwich made up of 50mm insulation with a 2mm steel plate on top, and a finish of marmoleum that is slightly sprung. Davies says: 'In the science and technology rooms we are going for a pour-on seamless resin-base finish, and in the gym, drama space and the assembly hall a sprung Junckers floor.' The ceilings in the classrooms are the painted soffits of the TermoDeck planks - a requirement of the TermoDeck system. In corridors there are to be suspended metaltile ceilings with plasterboard margins beneath runs of ducting. On the floors is Flotex. Davies says: 'It's a very hardwearing man-made sheet material - though it's not a carpet. It's very good for removing all kinds of things, including chewing gum.' The architect is still looking at the lighting, much of which has to be recessed where there are suspended ceilings, and at vanity units, cubicles and ceramic tiling - although Armitage Venesta has been selected for the WC systems and hand basins.

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